The side charging handle option for AR-15 is preferred by some shooters for multiple reasons. It is in very high demand by left-handed tactical and competition shooters because it allows them to operate at high speed. Left-handed shooters generally reload with the left hand on the pistol grip and the right hand on the magazine. When the shooter fires until the magazine is empty, and the bolt is locked to the rear, it is commonly awkward to find the bolt release button in the conventional location. The side charging handle allows the left-handed shooter to seat the magazine with his right hand, then pull the side charging handle to the rear approximately ½" and release it to allow the bolt to move forward and chamber a round. This is a very quick maneuver: seat mag, pull and release charging handle, resume firing. It is all done on the right side of the firearm and is all done with the right hand. The left hand remains in a firing position on the pistol grip and does not have to search for the bolt release button on the left side of the receiver. It also eliminates the awkwardness some left-handed shooters go through when trying to operate the conventional AR-15 charging handle, whether or not it is equipped with an ambi-release latch.

The AR-15 side charging handle mounts on the right side of the bolt and protrudes out of the right-hand ejection port by about ¾". This means you lose the conventional dust cover feature of the AR-15. It also requires a slot be machined into the receiver behind the ejection port. This exposes more of the receiver to contaminants, so it may not be a good option for those in blowing sand environments.

The side bolt handle is directly attached to the bolt carrier, so it reciprocates with the bolt carrier. It also means the side handle can be used as a forward assist and for quiet manual bolt operation.

For emergency responders operating in heavily occupied environments who don't chamber a round until firing appears to be a high probability, the side charging handle allows for very quick manipulation by left or right handled shooters.

Safety Note:
Always keep your muzzle pointed in a safe direction when you chamber a cartridge in your AR-15 style firearm. It has a free floated firing pin which generally makes light contact with the primer upon chambering a cartridge.

Right or left handed prone shooters firing specialty cartridges in a single shot method of operation prefer the side charging handle because it allows them to control the bolt's chambering force when loading single rounds into the chamber. It also allows very quick bolt manipulation without the awkwardness of operating the conventional charging handle or searching for the bolt release button.

The side charging handle option does not interfere with the function of the standard charging handle.